EP3574826A1 - Détection tactile basée sur la réponse en fréquence d'un tissu - Google Patents

Détection tactile basée sur la réponse en fréquence d'un tissu Download PDF

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Publication number
EP3574826A1
EP3574826A1 EP19177055.1A EP19177055A EP3574826A1 EP 3574826 A1 EP3574826 A1 EP 3574826A1 EP 19177055 A EP19177055 A EP 19177055A EP 3574826 A1 EP3574826 A1 EP 3574826A1
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Prior art keywords
electrode
distal
impedance
tissue
magnitudes
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EP19177055.1A
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German (de)
English (en)
Inventor
Assaf Govari
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Biosense Webster Israel Ltd
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Biosense Webster Israel Ltd
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/1206—Generators therefor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14—Probes or electrodes therefor
    • A61B18/1492—Probes or electrodes therefor having a flexible, catheter-like structure, e.g. for heart ablation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
    • A61B5/0538—Measuring electrical impedance or conductance of a portion of the body invasively, e.g. using a catheter
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor
    • A61B5/279—Bioelectric electrodes therefor specially adapted for particular uses
    • A61B5/28—Bioelectric electrodes therefor specially adapted for particular uses for electrocardiography [ECG]
    • A61B5/283—Invasive
    • A61B5/287—Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
    • A61B5/6867—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive specially adapted to be attached or implanted in a specific body part
    • A61B5/6869—Heart
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
    • A61B5/6885—Monitoring or controlling sensor contact pressure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00315—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00345—Vascular system
    • A61B2018/00351—Heart
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00571—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for achieving a particular surgical effect
    • A61B2018/00577—Ablation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00571—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for achieving a particular surgical effect
    • A61B2018/00595—Cauterization
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00636—Sensing and controlling the application of energy
    • A61B2018/00773—Sensed parameters
    • A61B2018/00875—Resistance or impedance
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/1206—Generators therefor
    • A61B2018/128—Generators therefor generating two or more frequencies
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/064—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension
    • A61B2090/065—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension for measuring contact or contact pressure

Definitions

  • the present invention relates generally to intrabody medical procedures and instruments, and particularly to cardiac electro-anatomical sensing and ablation.
  • U.S. Patent Application Publication 2016/0287137 describes a method and system for assessing electrode-tissue contact before the delivery of ablation energy.
  • the method may generally include determining a difference between a maximum impedance magnitude at a low frequency for a given electrode and an absolute minimum impedance magnitude at the low frequency across all electrodes, determining a difference between a maximum impedance magnitude at a high frequency for a given electrode and an absolute minimum impedance magnitude at the high frequency across all electrodes, and determining a difference between a maximum impedance phase at the high frequency for a given electrode and an absolute minimum impedance phase at the high frequency across all electrodes.
  • These differences may be correlated to one another using a linear model, the results of which determining whether the given electrode is in contact or not in contact with tissue.
  • U.S. Patent Application Publication 2016/0278841 describes a medical instrument that comprises an elongate body having a proximal end and a distal end and a pair of electrodes or electrode portions, for example a split-tip electrode assembly.
  • Systems and methods are described that perform contact sensing and/or ablation confirmation based on electrical measurements obtained while energy of different frequencies is applied to the pair of electrodes or electrode portions.
  • the contact sensing systems and methods may calibrate network parameter measurements to compensate for a hardware unit in a network parameter measurement circuit or to account for differences in cables, instrumentation or hardware used.
  • An embodiment of the present invention provides a method including measuring a first impedance-magnitude between a distal-electrode fitted at a distal end of a medical instrument in an organ of a patient and a surface-electrode attached externally to the patient, at a first electrical frequency.
  • a second impedance-magnitude between the distal-electrode and the surface-electrode is measured at a second electrical frequency.
  • a difference between the first and second measured impedance-magnitudes is calculated. Based on the calculated difference, an indication of, whether the distal-electrode is in physical contact with tissue or immersed in blood is decided, and outputted.
  • the method includes comparing the calculated difference to a given threshold, and deciding that the distal-electrode is in touch with tissue if the difference is larger than the given threshold.
  • the method includes measuring at the first electrical frequency a first set of impedance-magnitudes and measuring at the second electrical frequency a second set of impedance-magnitudes, wherein calculating the difference comprises calculating multiple differences between the respective first and second impedance-magnitudes, and wherein deciding whether the distal-electrode is in physical contact with tissue comprises making a decision based on the multiple calculated differences.
  • the method further includes measuring the first and second sets of impedance-magnitudes by a plurality of distal-electrodes.
  • the method further includes fitting one or more statistical distributions to the multiple calculated differences.
  • One or more statistical tests are applied to the distributions. Based on results of the one or more statistical tests, whether a calculated difference among the respective set of differences is statistically significant is deduced. Based on whether the calculated difference is statistically significant, whether the distal-electrode is in physical contact with tissue or immersed in blood is decided.
  • the first electrical frequency equals 1.5KHz or lower, and wherein the second electrical frequency equals 20KHz or higher.
  • the method includes denoting the indication on an electro-anatomical map.
  • a system including an electrical interface and a processor.
  • the electrical interface is configured for communicating with a distal-electrode fitted at a distal end of a medical instrument in an organ of a patient.
  • the processor is configured to receive, via the electrical interface, (i) a first impedance-magnitude measured between the distal-electrode and a surface-electrode at a first electrical frequency, and (ii) a second impedance-magnitude measured between the distal-electrode and the surface-electrode at a second electrical frequency.
  • the processor is further configured to calculate a difference between the first and second measured impedance-magnitudes, and based on the calculated difference, decide, and output an indication of, whether the distal-electrode is in physical contact with tissue or immersed in blood.
  • a catheterization procedure of an organ of the body such as cardiac electro-anatomical mapping and/or ablation
  • an electrode fitted at a distal end of a medical instrument such as a catheter
  • a contact force sensor at the distal end of the catheter may be used.
  • the need to use a dedicated sensor might cause the catheterization procedure to be cumbersome and time-consuming, and also increase the size and cost of the catheter.
  • Embodiments of the present invention that are described herein provide methods and systems for determining whether a distal-electrode of a catheter is in physical contact with tissue of an organ, such as cardiac tissue, by using the distal-electrode itself without additional hardware.
  • tissue of an organ such as cardiac tissue
  • physical contact can be even verified using the same electrical signals that the electrode applies and/or senses.
  • the physical contact can be determined while the electrode is used for performing other tasks, such as impedance-based position measurement, electro-anatomical sensing of cardiac tissue and/or ablation.
  • distal-electrode For clarity and simplicity, the description that follows refers to a single distal-electrode. Alternatively, any suitable number of distal-electrodes may be fitted to a catheter, and there can be more than one catheter in the heart in parallel that employ the disclosed method.
  • embodiments of the present invention utilize measurements of the magnitude of the electrical bio-impedance between the distal-electrode and one or more body-surface electrodes. This magnitude is referred to hereinafter as 'impedance-magnitude.' The dependence of the impedance-magnitude on electrical frequency provides an indication of whether or not the distal-electrode is in direct physical contact (i.e., touches) the cardiac tissue.
  • a processor analyses the frequency-dependent difference in impedance-magnitude to determine whether the distal-electrode is in touch with tissue or is in blood. For determining contact, the processor may apply any suitable criterion, such as check whether the difference in impedance-magnitude exceeds a given threshold.
  • the distal-electrode is used for injecting and/or measuring frequency dependent electrical signals (e.g., voltages and/or currents and/or impedances).
  • frequency dependent electrical signals e.g., voltages and/or currents and/or impedances.
  • the electrode injects the signals one or more surface-electrodes are used for measuring the frequency dependent signals.
  • voltages modulated at different frequencies are applied between the surface-electrodes, and the distal-electrode is used for measuring resulting signals. Either way, the processor analyzes the measured frequency-dependent signals, and determines whether the distal-electrode is in physical contact with cardiac tissue or immersed in blood.
  • the processor performs statistical analysis of multiple measured frequency-dependent impedance-magnitudes, for providing robust indication of physical contact of the distal-electrode with tissue.
  • the processor may apply any suitable statistical test (e.g., t -test), and provide the test-result. If a given indication per a given distal-electrode passes the statistical test as a statistically significant one, then the processor compares the indication to a criterion, such as a preset threshold of change in impedance-magnitude between given low and high frequencies, so as to determine whether the specific distal-electrode is in touch with tissue or immersed in blood.
  • a criterion such as a preset threshold of change in impedance-magnitude between given low and high frequencies
  • the disclosed technique is used in a catheter based electro-anatomical mapping and ablation system, which uses the distal-electrode for determining locations where arrhythmia may originate from or propagate through, for diagnostic purposes and/or for enabling a physician to decide whether to ablate selected locations on an inner surface of the heart.
  • the disclosed technique eliminates the need for dedicated sensors and other hardware for detecting physical contact of an electrode with tissue. Avoiding additional system resources and eliminating the need to package additional sensors into the limited space of a catheter distal end may simplify catheters and/or catheter-based systems. As a result, cardiac diagnostic and therapeutic systems can be simplified. The disclosed techniques may also simplify and further improve the clinical outcome of diagnostic and therapeutic procedures.
  • Fig. 1 is a schematic, pictorial illustration of an electro-anatomical mapping system, in accordance with an embodiment of the present invention.
  • Fig. 1 depicts a physician 27 using an electro-anatomical catheter 29 to perform an electro-anatomical mapping of a heart 23 of a patient 25.
  • Catheter 29 comprises, at its distal end, one or more arms 20, which may be mechanically flexible, to each of which are coupled one or more distal-electrodes 22.
  • electrodes 22 acquire and/or inject signals from and/or to the tissue of heart 23.
  • a processor 28 receives these signals via an electrical interface 35, and uses information contained in these signals to construct an electro-anatomical map 31.
  • processor 28 may display electro-anatomical map 31 on a display 26.
  • a tracking system is used to track the respective locations of distal-electrodes 22, such that each of the signals may be associated with the location at which the signal was acquired.
  • ACL Active Current Location
  • a processor estimates the respective locations of the electrodes based on impedances measured between each of distal-electrodes 22 and a plurality of surface-electrodes 24 that are coupled to the skin of patient 25.
  • three surface-electrodes 24 may be coupled to the patient's chest, and additional three surface-electrodes 24 may be coupled to the patient's back (For ease of illustration, only one surface-electrode is shown in Fig. 1 ).
  • electrodes 22 are inside heart 23 of the patient, electric currents are passed between electrodes 22 and surface-electrodes 24.
  • processor 28 Based on the ratios between the resulting current amplitudes measured at surface-electrodes 24 (or between the impedances implied by these amplitudes), and given the known positions of electrodes 24 on the patient's body, processor 28 calculates an estimated location of each of electrodes 22 within the patient's heart. The processor may thus associate any given impedance signal received from electrodes 22 with the location at which the signal was acquired.
  • processor 28 is further configured to estimate and verify the quality of physical contact between each of electrodes 22 and an inner surface of cardiac chamber during measurement.
  • the indication is based on modeling the frequency response of the impedances sensed by each of electrodes 22, which is different for blood and for tissue, and thus may serve as indication of physical contact, as elaborated below.
  • Impedance based measurements can also be done by applying voltage gradient using surface-electrodes 24 or other skin attached electrodes, use electrodes 22 for measuring voltages induced in the heart relative to a reference surface-electrode.
  • One example of such a system is the Carto®4 technology produced by Biosense-Webster, Inc. (Irvine, California).
  • embodiments of the present invention apply to any position sensing method in which electrodes apply and/or measure modulated electrical signals.
  • sensing and/or therapeutic catheters such as the SmartTouch®, the Navistar® and the Lasso® Catheters (produced by Biosense-Webster, Inc.) may equivalently be employed.
  • Contact sensors may be fitted at the distal end of electro-anatomical catheter 29.
  • other types of electrodes such as those used for ablation, may be utilized in a similar way to electrodes 22 for acquiring the needed frequency dependent impedance data.
  • an ablation electrode used for collecting frequency dependent impedance data is regarded for that matter in the description as a distal-electrode.
  • processor 28 may be embodied as a single processor, or as a cooperatively networked or clustered set of processors.
  • Processor 28 is typically a programmed digital computing device comprising a central processing unit (CPU), random access memory (RAM), non-volatile secondary storage, such as a hard drive or CD ROM drive, network interfaces, and/or peripheral devices.
  • Program code, including software programs, and/or data are loaded into the RAM for execution and processing by the CPU and results are generated for display, output, transmittal, or storage, as is known in the art.
  • the program code and/or data may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.
  • Such program code and/or data when provided to the processor, produce a machine or special-purpose computer, configured to perform the tasks described herein.
  • Fig. 2 is a schematic graph illustrating the frequency dependence of the impedance-magnitude of cardiac tissue vs. blood, in accordance with an embodiment of the present invention.
  • the impedance-magnitude of cardiac tissue as a function of frequency is given by a curve 50.
  • the impedance-magnitude of blood as a function of frequency is given by a curve 51.
  • the largely frequency independent blood impedance-magnitude depicted by curve 51 is about 100 ⁇ .
  • Cardiac tissue impedance-magnitude, as depicted by curve 50 is typically several times higher at the low end of frequencies (in some cases, approximately 300 ⁇ ), and becomes similar to blood at the higher end of frequencies.
  • tissue impedance-magnitude is strongly frequency dependent approximately between 1kHz and 30kHz.
  • Another example of a characterized frequency dependence of impedance-magnitude of blood vs. that of a body tissue is provided in " Medical Instrumentation: Application and Design," Webster (ed.) 3rd Ed., John Wiley & Sons, Inc., New-York, 1998 .
  • impedance varies with frequency when the current flows through tissue because tissue cells permit passage of the high frequency (while absorbing some of its energy).
  • blood plasma fluid
  • distal-electrode 22 is in good physical contact with cardiac tissue (as opposed to being immersed in blood), the resulting difference in impedance-magnitudes measured using that electrode (as a function of frequency) should be noticeable.
  • ACL system 20 measures a set of impedance-magnitudes
  • the impedance values Z jk ( ⁇ l ) and Z jk ( ⁇ h ) are complex values having both magnitudes and phases.
  • disregard the phase information.
  • the frequency ⁇ l is a first, given low frequency
  • frequency ⁇ h is a second, given high frequency, of an injected modulated current.
  • the index k counts repeated measurements.
  • processor 28 compares the differences between impedance-magnitudes to a criterion, such as a given threshold having a value R 0 , such that if a difference in impedance-magnitudes exceeds R 0 then the processor determines the distal-electrode is in contact with cardiac tissue.
  • a criterion such as a given threshold having a value R 0
  • processor 28 performs statistical analysis of the numerous differences of impedance-magnitudes calculated from measurements, for providing robust indication of a physical contact of an electrode with tissue.
  • one or more statistical distributions e.g., Normal distributions
  • processor 28 may be fitted to the calculated impedance-magnitudes differences, such as ⁇
  • the processor now applies a statistical test (e.g., t-test) to the distributions.
  • a statistical test e.g., t-test
  • the processor compares the difference to a criterion, such as a threshold difference between impedance-magnitudes having a value R 0 . If the calculated difference of impedance-magnitudes is below R 0 , then the processor may update the system, for example by denoting in an electro-anatomical map, with the information that the specific distal-electrode is in touch with blood. If the calculated difference of impedance-magnitudes is above R 0 , then the processor updates the system, with the information that the specific distal-electrode is in touch with tissue, for example by denoting that as a touched location on a map.
  • a criterion such as a threshold difference between impedance-magnitudes having a value R 0 . If the calculated difference of impedance-magnitudes is below R
  • the impedance-magnitude of tissue as a function of frequency varies mostly between about 1KHz and 30KHz.
  • the low frequency, ⁇ l equals 1.5KHz or less
  • the high frequency, ⁇ h equals 20KHz or more.
  • Selecting the low and high frequencies the way detailed above increases the robustness of impedance-magnitude measurements.
  • robust measurements increase the validity of statistical tests to determine in a statistically significant manner if a calculated difference in impedance-magnitude is an indication of contact with tissue, an indication of contact with blood, or an insignificant result to be ignored.
  • the numerical values of the high and low frequencies given above are chosen purely by way of example. In alternative embodiments, any other suitable frequencies values can be used.
  • each distal-electrode, out of one or more distal-electrodes 22, senses modulated voltages that were applied between pairs of surface-electrodes 24, at a first frequency, ⁇ l , and a second frequency, ⁇ h . Therefore, the general touch detection principle described herein is applicable with electrodes either applying and/or sensing modulated electrical signals.
  • Fig. 3 is a flow chart that schematically illustrates a method for sensing physical touch between an electrode and cardiac tissue, in accordance with an embodiment of the present invention.
  • physician 27 inserts electro-anatomical catheter 29 into the heart, deploys and engages tissue of heart 23 at a given location.
  • the process may then begin with processor 28 of system 20 measuring sets of impedance-magnitudes between distal-electrodes 22 and surface-electrodes 24 at low and high frequencies, at a measurement step 62.
  • the low frequency is chosen below 1.5KHz
  • the high frequency is chosen above 20KHz.
  • any other suitable low and high frequencies can be used.
  • processor 28 calculates, for each distal-electrode 22, an associated set of differences in impedance-magnitudes between impedance-magnitudes measured at low and high frequencies.
  • processor 28 fits to all impedance-magnitude differences one or more statistical distributions and applies one or more statistical tests, to determine whether impedance-magnitude differences (associated each with an individual distal-electrode 22) are statistically significant.
  • processor 28 drops the result (i.e., ignores it), at a dropping step 70. If the calculated difference is statistically significant, then processor 28 applies a suitable criterion, such as comparing the difference to a threshold having a value R 0 , at a comparing step 72. If the calculated difference of impedance-magnitudes is below R 0 , then processor 28 updates the system, at a blood decision step 74, with the information that the specific distal-electrode 22 is immersed in blood and not in touch with the cardiac tissue. If the calculated difference of impedance-magnitudes is above R 0 , then processor 28 updates the system, at a tissue decision step 76, with the information that the specific distal-electrode 22 is in touch with cardiac tissue.
  • a suitable criterion such as comparing the difference to a threshold having a value R 0 .
  • the procedure may be repeated several times for the same location, or move to another location on the inner surface of heart 23 by moving the catheter.
  • the method may then return to step 62.
  • step 66 may be omitted, for example if measurement results have a sufficiently large signal to noise ratio. The process then goes directly from step 64 to step 72.

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EP19177055.1A 2018-05-29 2019-05-28 Détection tactile basée sur la réponse en fréquence d'un tissu Withdrawn EP3574826A1 (fr)

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US15/991,291 US20190365463A1 (en) 2018-05-29 2018-05-29 Touch detection based on frequency response of tissue

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EP (1) EP3574826A1 (fr)
JP (1) JP2019205831A (fr)
CN (1) CN110537970A (fr)
AU (1) AU2019203666A1 (fr)
CA (1) CA3044179A1 (fr)
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US11931182B2 (en) 2019-12-09 2024-03-19 Biosense Webster (Israel) Ltd. Catheter with plurality of sensing electrodes used as ablation electrode
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